IS IT 2014 YET? Terry Collins argues with umpire Jerry Layne after Atlanta’s Freddie Freeman was ruled safe at first base on an apparent blown call in the Mets’ 4-1 loss to the Braves in 10 innings yesterday. Photo: Paul J. Bereswill; SNY

DOWN AND OUT: Atlanta’s Jason Heyward is looked at by a trainer after being hit in the jaw with a Jon Niese pitch yesterday. (Paul J. Bereswill)

Mets left-hander Jon Niese displayed a tragic flaw yesterday.

He showed he was human. Hey, he gave up a run.

Niese, in his third start since returning from the disabled list, pitched seven powerful innings against the Braves. But he surrendered that one run — which came shortly after he nailed Atlanta’s Justin Heyward in the jaw with a fastball.

“It was tough. I wanted to elevate a fastball right there [but] it kind of ran in on him. Obviously no intent but I just felt bad. It’s every pitcher and every hitter’s worst nightmare,” Niese said. “Just hope he’s OK.”

See? Human. But the human element that ultimately led to the Mets’ 4-1 downfall in 10 innings came in the form of what replays showed was an apparent blown call at first base. After umpire Jerry Layne ruled Atlanta’s Freddie Freeman was safe instead of being the third out on a deflected hit to the mound, Chris Johnson unloaded on the very next pitch and drove a three-run homer to left.

“Jerry just said he thought he got it right. I didn’t have much to say that was very nice,” said Mets manager Terry Collins, who was ejected after Johnson’s homer for those not nice words, uttered when he tried to save second baseman Daniel Murphy (too late, Murphy also was tossed).

“We had a difference of opinion,” said Murphy, who claimed “my difference of opinion started as soon as the ball went in the air off Johnson’s bat.”

Next year, perhaps the Mets would have challenged under the new replay rules and the game would have continued. But this is 2013 and managers don’t get to toss red flags. So the Mets wasted a masterful effort by Niese, who received only a solo homer by Josh Satin in the fourth inning as offensive support.

“Another great outing by Jon,” Collins said. “His cutter today was the best he’s had.”

Niese, who struck out nine, gave back the one run in that frightful sixth. With two out, he wanted a 1-2 fastball in on Heyward. It sailed up and crashed into Heyward’s jaw, possibly getting a piece of the helmet flap. Heyward went down. He suffered a fractured jaw and will be out 4-6 weeks.

“I felt horrible. Sometimes this game can be pretty dangerous,” Niese said. “I felt terrible but at the same time I had to regroup.”

Niese, who assured Collins he was not affected and could pitch, surrendered singles to Andrelton Simmons and Freeman with the latter getting the RBI.

The eruptions came in the 10th after the Mets squandered a bases-loaded situation in the ninth. With two out in the 10th, reliever Scott Atchison (3-2) yielded a single to Simmons. Scott Rice came on to face Freeman who rapped back to the mound. Rice deflected, retrieved and threw, but was apparently too late.

“I should have fielded it. It came at me and just tipped off my glove. I thought the ball beat him to first, but it was really close,” Rice said.

Greg Burke was summoned to face Johnson. His pitch was off the plate — and landed in the seats.

“We were trying to come in there on Chris, and we’d been doing it all game. It was basically where I wanted to put it,” Burke said. “It was up a little bit.”

And out a lot. The Braves summoned Craig Kimbrel, who notched his 40th save, converting a team-record 30th straight chance.

“Getting a run off him is tough enough and we had to get three,” Satin said. “I thought we got him. I thought the ball was in my glove before he hit the bag.”